"We're not stealing," announces Jennifer Pick at the outset of this hour-long piece, created by theatre company Getinthebackofthevan and performed with Lucy McCormack. It's a response to Internal, by Belgian theatre company Ontroerend Geod, an intimate and boundary-breaking work that caused a sensation at the 2009 Edinburgh festival for encouraging audiences to reveal their innermost feelings, sometimes with disturbing results. As TS Eliot knew, sometimes it's better to steal than merely borrow, but External presents an evening of ironic navel-gazing instead.

The piece is part of an increasingly prevalent trend: performance about performance. Self-referential theatre can be fun, and External is playful, exuberant, even rather sweet as it explores the divide between performers and audiences, tinkers with convention, and frequently implores us not to leave. But because it demands that its audience is already au fait with traditional and more experimental theatre, particularly the work of Forced Entertainment and some immersive companies, this feels like a dialogue theatre is having with itself – or this bright young company is having in public about its own future.

The future of theatre is an interesting subject to consider, and there is fun to be had recognising the references, enjoying the in-jokes about embracing the chaos, singling out the audience for praise, and counting down the duration of the performance. It's a show that will certainly win a following from other theatre-makers and performance studies students. But why set out to speak to so few, when there exists a much bigger audience hungry for daring, relevant, radical theatre that looks beyond the four walls of the theatrical black box?